Several mammalian virus vectors are in human clinical trial to evaluate their potential as HIV vaccine delivery platforms, but these vectors also have significant drawbacks that include safety concerns, high production and purification costs, and a host cell tropism that is often very broad. In contrast,bacteriophage vectors are cheap to manufacture and purify, and can be selectively targeted to mammalian cells through engineered modifications of the phage coat proteins. The central hypothesis of this Innovation grant application is therefore as follows: (i) that bacteriophage vectors can be retargeted so as to allow efficient transduction of dendritic cells (DC), and (ii) that these modified bacteriophage vectors can be used to elicit specific and potent immune responses to an encoded (HIV-1) antigen. This hypothesis will be tested experimentally, in a proof-of-principle study, through three specific aims. In the first aim, modified bacteriophage vectors capable of transducing DC will be generated, using multiple complementary approaches. To do this, a mammalian GFP reporter cassette will be inserted into our phage vectors, and these GFP-phage will then be subjected to specific coat protein modifications intended to enhance phage uptake into DC; a series of complementary approaches that will be evaluated in parallel in order to determine the optimum approach. In the second specific aim, an HIV-1 gene insert will be introduced into the genomes of the DC-targeted phage vectors, and their ability to express HIV-1 antigens in DC will be evaluated. Finally, in Aim 3, the most promising HIV-1 antigen-encoding phage vectors will be inoculated into BALB/c mice and into guinea pigs, together with relevant control phage, and their ability to elicit HIV-1-specific cellular and humoral immune responses will be examined. These experiments will also include studies to determine the effectiveness of multiple immunizations with phage vectors (i.e., to test whether anti-phage antibodies induced after an initial immunization have an impact upon subsequent boosting with the same phage, or different/modified phage). [unreadable] [unreadable]